In general, I'm in favor of colorblind casting, but:
- I'm pretty sure this wasn't actually colorblind casting, and,
- I don't believe in using colorblind casting for movies based on canon in which characters' races (or appearances in general) are clear. Think about it - do you think the casters of the Harry Potter movies just crossed their fingers and hoped that the actor best suited to play Ron would be a redhead? Of course not.
The creators of this movie took a world with, I understand, mostly Asian characters, and cast white people for all of the heroes and a person of color ONLY FOR THE VILLAIN. (Really?) This is a shame on several levels. From the previews, the movie screams, "generic blockbuster fantasy." I love fantasy, and I have to say that a little diversity (um, accuracy) in the casting would, even aside from being the right thing to do, have made the movie stand out. People of color as heroes in fantasy are, unfortunately, quite rare.
I don't have a lot more to say about this - or rather, you don't need to hear me spout off again about whitewashing - but I refer you to the comic-strip response of Gene Luen Yang, author of American Born Chinese.